Thomas Hutchinson pleaded guilty to 55 charges on Tuesday in Middlesex Superior Court, including rape of a child by force, possession of child pornography, and attempted extortion.

Authorities say the 21-year-old Hutchinson contacted young girls on the Internet, pretended to be in the modeling industry, enticed the girls into sending him nude photos of themselves, then threatened to post the photos online unless they had sex with him.

An investigation was launched in 2011 in connection with a 15-year-old girl Hutchinson met online.

The Sun of Lowell reports that investigators found as many as 17 other victims during a search of the defendant's computers.